molecular geometry

Question 1

why is it important that we can predict the shape of molecules?

Answer 1

so we know how they interact with each other and other molecules

Question 2

what are the 2 types of pairs?

Answer 2

bonding pairs, lone pairs

Question 3

why do we assume electron pairs repel each other

Answer 3

electrons are negative so the region of space they occupy (orbital) is also negative. like charges repel so electron pairs must be furthest distance away from each other

Question 4

linear arrangement is…

Answer 4

… straight line

Question 5

2 bonding pairs is a … arrangement

Answer 5

linear

Question 6

what is the bond angle of a linear molecule?

Answer 6

180˚

Question 7

what is the name of a molecule with 3 bonding pairs?

Answer 7

trigonal planar

Question 8

what is the bond angle of a trigonal planar molecule?

Answer 8

120˚

Question 9

how do you draw 3D molecules

Answer 9

wedge = towards you
dashed line = away from you

Question 10

what are the bonding angles of a tetrahedral molecule?

Answer 10

109.5˚

Question 10

what is the name of a molecule with 4 bonding pairs?

Answer 10

tetrahedral

Question 11

as lone pair increase, bond angles…

Answer 11

decrease

Question 12

why do lone pairs repel more than bonding pairs

Answer 12

‘charge cloud’ isn’t shared between atoms so it has more freedom to move so is wider.

Question 13

state VSEPR theory

Answer 13

LpLp>LpBp>BpBp

Question 14

what does VSEPR theory stand for?

Answer 14

Valence Shell Electron Pair Repulsion Theory

Question 15

what is the name of a molecule with 2 bonding pairs and 1 lone pair?

Answer 15

bent

Question 16

what is the bond angle of a bent molecule?

Answer 16

118˚

Question 17

what’s the name of a molecule with 3 boning pairs and 1 lone pair?

Answer 17

trigonal pyramidal

Question 18

what is the bond angle of a trigonal pyramidal molecule?

Answer 18

107˚

Question 19

what is the name of a molecule with 2 lone pairs and 2 bonding pairs?

Answer 19

bent - same structure as 1 lone pair and 2 bonding pairs

Question 20

what is the bond angle of a bent molecule (2 Lp)?

Answer 20

104.5

Question 20

what is the name of a molecule with 5 bonding pairs?

Answer 20

trigonal bipyramidal

Question 21

what are the bond angles for a trigonal bipyramidal molecule?

Answer 21

120˚, 90˚

Question 22

why isn’t the bond angle for trigonal bipyramidal 180/5 ∴ 72˚?

Answer 22

they should be repelling as far as possible and the only way to do this is to have more than one plane so although they aren’t repelling equally, they’re repelling the max distance

Question 23

what is the name of the molecule with 4 bonding pairs and 1 lone pair?

Answer 23

trigonal bipyramidal but known as seesaw/sawhorse

Question 24

what are the bond angles of a seesaw molecule

Answer 24

87˚, 102˚

Question 25

what is the name of the molecule with 3 bonding pairs and 2 lone pairs?

Answer 25

trigonal bipyramidal/ t-shaped

Question 26

what is the bond angle in a t shaped molecule?

Answer 26

88˚

Question 27

what is the name of a molecule that has 2 bonding pairs and 3 lone pairs?

Answer 27

//////trigonal bipyramidal atomic shape but linear electron configuration

Question 28

how would you draw an octahedral molecule

Answer 28

straight lines above and below. 2 wedges each side bottom half. 2 dashed lines each side coming from top.

Question 29

whats the name of a molecule with 6 bonding pairs?

Answer 29

octahedral

Question 30

what is the bonding angle of an octahedral molecule?

Answer 30

90˚

Question 31

what is the name of a molecule with 4 bonding pairs and 2 lone pairs?

Answer 31

square planar

Question 32

what is the bond angle of a square planar and why is this?

Answer 32

still 90˚like octahedral because the lone pairs are positioned top and bottom

Question 33

what assumptions do we make when predicting the shape of a molecule?

Answer 33

- electron pairs repel to be as far apart as possible - lone pairs repel more than bonding pairs

Question 34

steps to predict the shape of a molecule

Answer 34

1) draw a dot and cross diagram 2) count number of electron pairs around the central atom 3) identify the electron pair arrangement 4) add in atoms and lone pairs

Question 35

what do we assume when predicting the shape of a molecule with double bonds?

Answer 35

- the electron pairs in a double bond don't repel each other and treat them as one

Question 36

if a molecule has single and double bonds, why doesn't the double bond cause extra repulsion?

Answer 36

double bonds repel a similar amount to single bond as any extra repulsion from pi bonds is cancelled out through sigma bonds as sigma bonds spend equal time above and below the atom

Question 37

when two atoms are a pair of electrons they exist in a ... bond?

Answer 37

sigma

Question 38

when two atoms share a second pair of electrons they exist in a ... bond

Answer 38

pi

Question 39

when drawing an ion that has a positive charge, the electron is removed from...

Answer 39

... the least electronegative ion

Question 40

when drawing an ion that has a negative charge, we add an electron to the...